As a frequent visitor and SPG guest in Doha, I thought I'd chime in... [repeatedly stayed in 3/4 of the SPG options there]

W: Easily the best W in Starwood's portfolio as it effortlessly blends awesome form with awesome substance. It opened back in 2009 but still manages to look incredible, trendy and relevant to this day and is holding up incredibly well. Constant upgrades every time as a Plat [I've now sampled all room types bar the Extreme Wow Suite], their WIP Lounge and free food/lounge perks/happy hour is a major stand out as W Hotels aren't designed to have lounges, their breakfast at Market is amazing, service is cool and professional and their spa is a class act, however expensive it is. Their pool is a bit of an afterthought but was just renovated and is leagues ahead of the old one, but still languishes in the shade due to the shape/design/layout of the building.

Westin: I love the W but this is the one that keeps me coming back. Massive new rooms [around two years old], absolutely excellent staff [Nadheema and Maja deserve particular shoutouts], very generous suite upgrades for Plats, spacious club lounge with great health-conscious presentations throughout the day with a great happy hour, huge spread at breakfast and wonderful pools and health club. All the style without the see-and-be-seen of the W; very highly recommended.

St. Regis: Got double-upgraded from a Deluxe Room to a Terrace Room to a John Jacob Astor Suite. Great facilities and a grand ambience, if a little anonymous. Staff are lovely, their breakfast is sumptuous, no happy hour or lounge perks so things can get pricey, location is a bit far, the pool is enormous and their Jacuzzi in the spa is worth the stay.

Hope this helps somehow!

khabah